According to the birthdates listed on the Supreme Court website, the court's nine current justices will have an average age of 75 by the time the next presidential term ends on Jan. 20, 2021.

Ruth Bader Ginsburg, the oldest justice, was born on March 15, 1933. She is now 82. When the next presidential term ends she will be 87 years and 10 months old -- or 87.8 years old.

Antonin Scalia, the second oldest justice, was born on March 11, 1936. He is now 79. When the next presidential term ends, he will be 84 years and 10 months -- or 84.8 years old.

Anthony Kennedy, the third oldest justice, was born on July 23, 1936. He is now 78. When the next presidential term ends, he will be 84 years and 5 months -- or 84.4 years old.

Stephen Breyer, the fourth oldest justice, was born on August 15, 1938. He is now 76. When the next presidential term ends, he will be 82 years and 5 months -- or 82.4 years old.

Clarence Thomas, the fifth oldest justice, was born on June 23, 1948. He is now 66 -- and will turn 67 next week. When the next presidential term ends, he will be 72 years and 6 months -- or 72.5 years old.

Samuel Alito, the sixth oldest justice, was born on April 1, 1950. He is now 65. When the next presidential term ends, he will be 70 years and 9 months -- or 70.8 years old.

Sonia Sotomayor, the seventh oldest justice, was born on June 25, 1954. She is now 60 -- and will turn 61 next week. When the next presidential term ends, she will be 66 years and 6 months -- or 66.5 years old.

Chief Justice John Roberts, the eighth oldest, was born on January 27, 1955. He is now 60. When the next presidential term ends, he will be 65 years and 11 months -- or 65.9 years old.

Elena Kagan, the youngest justice, was born on April 28, 1960. She is now 55. When the next presidential term ends, she will be 60 years and 8 months -- or 60.7 years old.

On Jan. 20, 2021, when the next president either takes the oath for a second term or relinquishes his or her office to a successor, the collective age of the 9 current Supreme Court justices will be 675.8 years.

Their average age will be 75 years.

If these nine current justices were to retain their seats through the next two presidential terms -- whether those terms were held by one president who was re-elected or by two different presidents -- their average age at the end of that second term would be 79 years.

The four oldest justices -- Ginsburg, Scalia, Kennedy and Breyer -- would be a collective 339.4 years when the next presidential term ends. Their average age would be almost 85 (84.85). If they stuck it out for two more terms, their average age would by almost 89.

The six oldest justices -- Ginsburg, Scalia, Kennedy, Breyer, Thomas and Alito -- would be a collective 482.7 years by the end of the next presidential term. Their average age by then would be 80.45. By the end of the next two terms, in January 2025, their average age would be 84.45.

Many of the names on the court may change by the time the next two or three presidents have served out their terms. But will America be the same country?

If the history of recent decades is any indicator, that still may be decided by five elderly lawyers given lifelong tenure in a government job.